Method and apparatus for welding corrugated sheets to flat sheets



BEST AVAILABLE COP\ .June 27, 1939. c. DE GANAHL ET AL 2,163,590

mmnoo AND APPARATUS FOR WELDING coammnsn sanm's To FLAT sazm's Filed Sept. 9, 1937 4 Sheets-Sheet l //v vzlvrofis: T/wMssBJ/WEALE Y #1. zuzmw/m. 5 A#ORNEY BEST AVAILABLE com June 27, 1939. c DE :G HL r AL 2,163,590

KETHOD AND APPARATUS FOR WELDING CORRUGATED SHEETS TO FLAT SHEETS Filed Sept. 9, 1937 4 Sheets-Sheet 2 ATTORNEY BEST AVAILABLE COP;

June 27, 1939. 2,163,590

METHOD AND APPARATUS FOR WELDING CORRUGATED smzm's TO FLAT smears c. DE GANAHL ET AL Filed Sept. 9, 1937 4 Sheets-Sheet 3 //V YE IV 7' 0/?8 THO/11175 5.1 HVEL 1. E, Gfl/Pl. gzfi/mwm.

ATTORNEY BEST AVAILABLE com June 27, 1939. DE GANAHL ET AL 2,163,590

umuon AND APPARATUS FOR WELDING connuexrzn SHEETS TO FLAT susms Filed Sept. 9, 1937 4 Sheets-Sheet 4 l/VVE/V TORS #001175 5. LJVELLE 637/? DEfi/YIV/Y/IL wwxmwu an ATTORNEY .larly advantageous in m'odern aircraft with corto provide a welding apparatus in which succes- Patented June 27, 1939 UNITED STATES PAT ENT OFFICE METHOD AND APPARATUS FOR WELDING CORRUGATED SHEETS T FLAT SHEETS Carl de Ganahi, Bristol, and Thomas B. Lavelle, Langhorne, Pa., assignors to Fleetwings, Inc Bristol, Pa., a corporation of Delaware Application September 9, 1937, Serial No. 163,018

40 Claims. (Cl. 2194) This invention relates to methods and apparation of the work and an electrode, when a limit tus for welding corrugated sheets to flat sheets. has been reached; to provide means and a In aircraft there are many situations where a method for welding relatively corrugated and uncomposite sheet composed of flat and corrugated corrugated sheets together so as to crowd extra sheets can be used to excellent advantage. Sheets metal in the uncorrugated sheet between corrugaof hard resilient stainless steel, aluminum tion peaks, whereby bending ofthecompositesheet Alclad and the like, for instance, are particuenables the uncorrugated sheet to be substantially continuously curved; to provide a continuously curved composite sheet; and many other objects and advantages as will become more apparent as the description proceeds. 1

Inthe accompanying drawings, forming part of this description;

Fig. 1 represents a side elevation of the welding machine of this invention according to the preferred embodiment thereof,

Fig. 2 represents a front elevation, partially in section, of the welding machine of Fig. 1,

Fig. 3 represents an elevation, partially in section, of a fluid motor for vertically supporting and moving an electrode roller arranged for lateral movements as well,

Fig. 4 represents a fragmentary horizontal section through the fluid motor supports for both electrode rollers, showing the lateral adjusting screw for one of the supports,

Fig. 5 represents a fragmentary vertical section, partially in elevation, through an assembly of roller electrodes, flat and corrugated sheets, and supporting rods engaging in the corrugations,

Fig. 6 represents a fragmentary section through the supporting plates and rods of the table, showing the anchor permitting slight lateral shifting of the rod electrodes,

Fig. 7 represents a view similar to that of Fig. 5, with the addition of flat sheet distorting or crowding rods so arranged that the material between peaks of the electrodes is greater than the normal fiat distribution,

Fig. 8 represents a fragmentary elevation of the finished compound sheet of Fig. 7, bent into a continuously curved section,

Fig. 9 represents a fragmentary perspective of a guide plate for the table to align the rods of the table with the roller electrodes,

Figs. 10 and 11, represent, respectively, a fragmentary plan and elevation, partially in section,

of the end of the table, showing the tensioning means for the flat sheet,

Fig. 12 represents a wiring diagram for the machine assembly,

Fig. 13 represents a fragmentary elevation of an individual rod of the grid of rods, showing the peripheral recesses to receive the attaching rugated sheets comprised of arcuate corrugations, preferably of continuously curved surfaces, as the reinforcement for the planar sheets. In assembling such composite assemblies in the past it has been usual to dispose the flat sheet upon a support, to dispose the corrugated sheet in superimposed relation thereon, then to associate the two together by a series of spot welds, either spaced or overlapping in a seam, by roller electrodes respectively resting and running in the corrugation and engaging the flat sheet. Among other disadvantages attaching to this procedure was the propensity for the weld to take place off from the peak or apex of the corrugation, instead of in the stabilized symmetrical location exactly on the peak. The weakness and uncertainty of this procedure will be obvious.

It is among the objects of the invention; to provide a welding machine in which corrugated and plane sheets can be rigidly welded together with uniform strength and with great speed; to provide a-method of associating fiat and corrugated metallic sheets rigidly together; to improve welding-machines; to provide a control system of interlocking electrical instrumentalities for welding machines; to provide a welding apparatus with means for applying welding force to the electrode, means for causing relative motion between the work and welding electrode, with means controlling the flow of the welding current, with a controlling system so arranged that the flow of the welding current cannot occur until electrode force and relative motion have been secured, and so arranged that the electrode force cannot be removed nor relative motion stopped until after the welding current flow has been interrupted;

sively welding pressure is applied, relative motion between electrode and work is secured, welding current flow is initiated, and in which the interruption in welding is secured in reversely successive order; to provide a welding apparatus in which electrode pressure, relative motion between work and electrode and flow of welding current are controlled by a single manual agency; to provide in welding apparatus means for automatically reversing the direction of relative moclamps to maintain the unbroken cylindrical extent of the assembly,

Fig. 14 represents a diagrammatic plan of the The machine comprises an elongated table l0,

mounted on a plurality of supports or legs II, each terminating in a roller [2, resting and movable on stationary tracks l3 extending transversely of the machine and resting on the floor H. The table is held in a predetermined position relative to rails or tracks l3 by means-such as the transverse apertured plates I5 (at each end) each having preferably two or more sets or rows of aligned apertures 40 spaced on centers coinciding with the pitch of the corrugations being treated. A pin i6 is vertically disposed and pressed by spring I! into a given notch or aper ture in plate I5. Pin I6 is controlled by a link [8, bell crank 20, and horizontal link 2|, actuated by a handle 22 toward the center of the table. Preferably there is a registration plate and pin at each end of the table, as noted, and handles 22 are close to the table center for operation simultaneously with the transverse adjusting means shown in Fig. 2. This comprisespreferably a hand wheel 23 rigid with rotatable threaded shaft or screw 24, journalled in opposite legs I I, for rotation without axial movement relative to the table. The screw 24 passes through a fixed nut 25 mounted on the floor M. The whole provides lateral shifting of the entire table to bring the work successively in steps under the welding roller to be described.

In view of. the great length of the table and of the mass of metal which it carries, it is necessary that the remote or extreme ends of the table be caused to move in synchronism. A preferred and simple device for this purpose is shown in Fig.14. The table ID has an attached stop I toward one end and another stop 2 toward the other end, both close to the floor I 4 and preferably in the center.

A cable 5 extends from one side of stop I, say the front, about pulleys 3, and terminates at the rear side of stop 2. A second cable 6, which may either be independent or a continuation of the first mentioned cable 5 extends in the opposite direction from the other, or rear, side of stop I, about pulleys 4, to the other, or front, side of stop 2. The system of pulleys and cables is kept taut by suitable means such as by turnbuckles (not shown), or by the flexible hangers or stays I, or the like, connected to the floor [4. Movement of one end of the table as, for instance, the end carrying stop I, is automatically accompanied by an identical movement of. the other end of the table, carrying stop 2, because of the tension on and direction of movement of the cables, as will be clear.

The table ID has suitable longitudinal frame members 26, such as angle or channel units, which extend the full length of the table and at each end bend toward each other and toward the center in a V formation, as at 21. The table is provided with suitable transverse bracing and frame members 9 to form a rigid entity. A grid of electrically coupled plates or bars and rods is BEST AVAILABLE COP: 1

provided for removable and replaceable association with the table I0, predetermined as to size and spacing by the pitch of the particular corrugated sheets forming with the fiat sheets the work to be welded. Thus a plurality of narrow elongated supporting plates or bars 28 are held in parallel spaced relation and in intimate electrical association by spacing sleeves 8 surrounding a transversely extending bolt or tie rod l9 extending through the bars and clamping them all together in a rigid grid arranged for seating on the table I!) substantially in a horizontal plane. As will be later explained the grid of rods could be arcuate in cross section, in place of planar, if pre-curved assemblies were desired. In this case the rolling electrodes to be described will have radial movement relative to such grid. rather than perpendicular as shown. Plates or bars 28 have a flat upper face 29, and may be made of any desired material of high or low resistance as desired, although copper is preferred.

Extending longitudinally on top of plates 28 is the plurality of round low-resistance rods 30, preferably of copper, having such diameter as to substantially fit within the downward presented open corrugations 3| of a selected predeterminedly corrugated sheet 32. Each rod 30 is clamped more or less loosely to the appropriate or registering supporting plate or bar 28, so as to be capable of restrained but free lateral shift-1. ing within limits. This is accomplished, illusa tratively, by spring clamps 33, or the like, having a median semi-cylindrical portion 34 arranged to fit tightly and closely in a peripheral recess 39' in rod 30, to hold it against the upper plane surface 29 of the plate. The clamp or clip has shoulders 35 slidable on the upper plate surface by reason of the lateral clearance 36 afforded toward the top of the plate by the clamp 33. The lower part of the clamp comprises legs 31 extending below the plate and joined by the transverse bolt 38. The clamps are of conducting material such as copper so as to insure maintenance of electrical coupling between all of. the bars and rods of the grid.

The arrangement is such that slight inequalities of frictional resistances that might cause such binding or misalignment as to prevent the seating of a corrugated sheet upon rigid and immovable rods, are obviated or nullified by the elasticity, so to speak, of the individual rods of the grid of rods, each of which is capable of slight lateral shifting, as shown, Preferably as noted the rods 30 are electrically connected together, although obviously if desired the rods may be relatively insulated from each other, or arranged in groups of electrically connected rods, insulated from adjacent groups, It will be understood that a given aperture 40 in plate l5 corresponds to a given position of the mean center line or axis of a rod 30 in a predetermined selected grids It will be understood that a suitably corrugated- 21 of table ill, at each end, although but one will.-

DCbI AVAILABLE COP\ be described, having the tapering frame members 4|, continuations of the side frame members 26, has a transverse end plate 42 having a central hole 43. Upon plate 42, a screw jack 44, or the like, is mounted, comprising the stationary internally threaded nut 45, in which the threaded shank 46 is rotatable. The shaft 46 extends through opening 43 and has a loose coupling con nection 4! and a short extension 48 terminating in coupling end 59 arranged to receive a coupling pin A more or less elongated sheet of steel 39 has its end 52 bent about a cross strip 53 forming a terminal enlargement, which is disposed in a recess 54 of a clamp jaw element 55, extending substantially the full width of the sheet 39. A main jaw clamp element 56 has a flat surface to engage the sheet 39 on its opposite surface from that engaged by jaw 55. The main element is removably coupled by pin 5| to the extension 48 and to the axially movable tensioning device 46, and is removably engaged with clamp member 55 by a plurality of bolts 51. It will be understood that the opposite end of sheet 39 will' be similarly clamped, either to anchor the sheet or to furnish a tension from both ends at once if desired. The tensioning arrangement is such that a pull is delivered to sheet 39 substantially in the plane of the upper surfaces of the grid of rods, and suflices to pull the sheet into a condition of substantial planarity, wherein all normally retained hollows and twists and humps are pulled flat, without, however, placing such tension on the sheet as would establish a stressed condition during welding.

As the degree of tension is important, it may.

be desirable, as shown in Fig. 15, to introduce into the tension line, a scale or spring balance 49, so that a predetermined tension can be given to the work. The advantages of this will be obvious, especially when the dangers incident to variations in tension between similar parts are appreciated.

The welding electrode carriage of the apparatus is preferably suspended from an overhead frame 69 in fixed relation to the floor I4 and includes track members 6| extending substantially parallel to the rods in the table below. The carriage comprises a substantially rectangular open frame 62, having suitable cross members as desired, having upper supporting rollers 63. A rack 64 is mounted rigidly horizontally adjacent each track 6| in mesh with gears 65 mounted on a shaft 66 driven by a suitable variable speed mechanism, such for instance as a Reeves drive 61 through drive gear 68. The arrangement is such that the entire carriage 62 can be positively driven forwardly or in reverse for the full length of the table, or of the desired portions thereof, or of the supporting track. In this connection it will be clear that suitable limit switches will be adjustably positioned to be engaged by portions of the traveling carriage. Thus a limit switch member I9 controlling a switch I65 or I16 is adjustable on track 6| to be engaged and tripped by a stop II on the carriage at each end of the track.

On one face of the traveling carriage there is rigidly mounted a vertical frame 12 carrying a fixed pneumatic cylinder I3 and forming a vertical guide 14' for the vertically reciprocable plunger controlled by a piston in cylinder I3. A second vertical frame 16, carrying cylinder 17 and plunger 18, is mounted on the frame or carriage for lateral adjustment, by any suitable means such as hand wheel 89 and screw 8| engaging a nut I9 on the rear of frame I6. The second frame 16 is held against vertical movement while siidable laterally, transversely of the table I9, on guide rail supports 82, Thus the frames can be relatively laterally adjusted to vary their spacing to accord with the pitch of the corrugations, and to the size and spacings of the rods of the grids, which are changed according to corrugation pitch changes. Practically and preferably there are at least four different corrugationpitches used, and each will be accomplished by replacement of the entire grid of bars and rods for the selectedpitch.

At the lower end of plunger I5, and in insulated relation thereto, is adjustably mounted the roller electrode journal block 83 in which a shaft 84 is freely rotatable, with its axis transverse of and substantially perpendicular to table I9 and rods 39 and the corrugations of a sheet mounted thereon. Shaft 84 carries the electrode roller 95 having a narrow peripheral contact area 96. Plunger I8 carries insulatedly the journal block 81 in which shaft 88 is rotatable and which carries roller electrode 99, having the narrow peripheral contact area 9|. The rollers 85 and 99 are preferably concentric and parallel and are so disposed that the respective narrow peripheral contact band of each is symmetrically above the apex of adjacent corrugations on the grid of rods 39. Suitable adjustments will be provided and it will. be understood that cylinders I3 and 11 will be so actuated, as by pneumatic pressure, as either to raise or positively and firmly to lower the respective rollers 85 and 99 to circuit closing engagement with sheet 39 superimposed upon corrugated sheet 32.

In addition to the surface irregularities of the supposedly flat sheet that might become impressed in some manner on the finished work if it were not placed under a preliminary tension, as previously described, it is found that welding such seams as are here contemplated, in the usual course, frequently results in distortions of various kinds, such as twists, undesired sheet convexities, and the like, where the roller electrodes are the principal means for forcing the sheets into intimate contacting relation. To insure an absence of such undesired distortions, heavy rollers of appreciable length and diameter are provided and arranged to float to their desired level in compressing association with the upper planar sheet. To this end, on each lateral side of the traveling carriage, there is pivoted at 92 an arm 94, having at its extreme end a journal 95 for a shaft 96 carrying a primary weighted roller 94', as of solid metal, free to float up and down in accordance with its reaction from the assembled work passing under it. Flattening roller 94' is disposed on the advancing or forward side of the electrode rollers 95 and 99, although preferably not too far away from the electrodes. A secondary rearward weighted roller 98 is supported on a shaft I99 extending through a slot MI in a bracket I92 mounted on arm 94, behind or on the other side of the electrode rollers 85 and 99 from roller 94'. It will be clear that secondary roller 99 may float in the slots I9I independently of the fluctuations of arm 94 responsive to movements of the roller 94'. Arm 94 has a guide bracket I93 slotted at I94 about a pin I95. Ihe slot I94 forms limits to the upward and downward adjustments of the rollers by movements of arms 94.

any desired manner, as by cables I95 connected by spring I96 to arm 94 and passing about drums I91 at each side of the carriage on a shaft I98 Such predetermined adjustments or movements of arm 94 are secured in' actuated by a worm wheel I I actuated by a worm III on shaft II2 driven by handle II3.

It being appreciated that after the sheets are superimposed and mounted on the table I0, the crank is turned and the weights disposed infioating rest on the work on each side of the electrodes and thus comprise rolling clamps. Owing to the wide expanse of metal pushed toward the plane of the table top (grid level), the welding taking place, as hereinafter explained, is in completely flattened untwisted sheet metal, so that the resultant product is a planar sheet to which a corrugated sheet is affixed.

The rolling clamp is primarily designed to maintain the position of component parts of the work remote from the welding, relative to the components of the work being welded during the welding operation. Thus the parts remote (disposed longitudinally between the rollers laterally for their full length) are held flat against the grid, during the welding of the work under the rolling electrodes, and the resulting finished work is therefor unwarped and is completely flat. 0bviously a change in the contour of the grid of rods, and of the rollers of the rolling clamp, say to an arcuate form (not shown) secures the same result exactly, and the finished work has a uniform, unwarped, non-distorted, arcuate formation after passing under such rolling clamp. In this latter case, with arcuate or curvilinear work the conforming rollers due to different diameters of different parts of the rollers might .have slipping relation with portions of the work, but this will make no particular difference.

As noted also the fluid operated pistons would in this latter case have a path of movement that was substantially radial of the grid, in place of the disclosed vertical movement. I

The traveling carriage carries everything necessary .to complete welding, except a source of electric power, which is lead to it by suitable connectors from an extraneous source. A welding timer II4 andwelding transformer 303 of suitable construction are mounted on the carriage and include leads II5 leading to block 83 and electrode roller 85, and connector H6 leading from roller electrode 90 and block 81 to the timer. The arrangement is preferably such as to produce automatic continuous series of spaced welding impulses in rapid succession, adjustable, for instance, to furnish welds at the rate of say 2, 4 or 8 welds per second as desired, as will be obvious to those skilled in the art. It will be obvious that with such series in relatively fixed timed relation the spacing of welds in the work will depend upon the speed of relative motion of the work and the electrodes. Thus by simply varying the speed of the drive for the traveling carriage, as noted, the weld lines will be comprised either of spaced independent welds or of overlapping welds forming a seam. The speed of travel of the carriage varies, illustratively, between 4.5 and 27 feet per minute, although other speeds can be secured if desired.

In order to secure a given or desired quasi-automatic action of the plungers for the roller electrodes, a solenoid-operated valve H1 is provided having suitable connections, so that when energized in one way it delivers compressed air or steam to both cylinders 13 and 11 at once to force the rollers 85 and 90 firmly against the work. When oppositely actuated it causes compressed fluid to enter the opposite ends of the cylinders to raise both plungers and rollers. Suitable valves and the like (not shown) are provided as to BESBMMBLE com enable independent operation of one roller electrode at a time if desired.

, To facilitate the operation of the mechanism a series of electrical instrumentalities are provided,

as follows: On the front of the carriage at points convenient to the operator there are a series of push button switches or circuit closures. At the bottom, preferably, for easy and quick location and operation, there is a stop button or other switch element I20. Above stop switch I20, are the start" switch I22, reverse" switch I24, and forward" switch I26.

At any desired location on the traveling crane or carriage it is preferred to place a series of visual indicators, such as electric lights, possibly of various colors, to impart predetermined information. Thus lamps I2I, I23, I25 and I21 may indicate that any given switch has been closed, or that an intermediate relay has a given position relative to its controlled circuit, etc. While the respective lamps may indicate the actuation of some or all of the respective named switches, it is preferred that one lamp, such as I2I, illustratively, indicate that the welding current is on or off, according to its indication, lamp I23 indicates that the device is ready to weld, while lamps I25 and I21 respectively indicate forward and reverse" travel of the carriage according to the closing of the manual switches or the limit switches previously discussed.

For convenience the switches are provided in duplicate on each side of the carriage, although preferably only a single set of signal devices is used. Obviously the signal device may be omitted, may be in duplicate, or may be arranged to designate difierent electrical situations than those recited, and may be of any nature such as of different colors as noted, or may be audible instead of, or in addition to, visual.

It is preferred that certain switches have dual functions. Thus switch I22, the starting switch, is arranged to be actuated three successive times to secure the 'proper coordinated orderly sequence of operations necessary to start the device welding.

Referring to the diagram it will be understood that 220 V. three phase alternating current is provided by leads I30, I3I, and I32, controlled by a master switch I33. A spot-welding timing device of conventional nature is indicated at H4, connected to leads I3I or I32, to line I30 through common connections, either directly or through switch 304 (hereinafter described).

This timer by means of contactors 30I, 302 permits a given timed current to pass through the welding transformer 303 at regular intervals depending on the number of contactors and the speed of the motor drive, which is preferably at the rate of either 2 or 4 impulses per minute, although other speeds are easily available and are contemplated. The welding current flows through roller electrodes 85 and 90 only when main welding contactor 304 is closed.

A three position sequential relay I35 has an operating coil I36 arranged to actuate switch 204 each time it is actuated and arranged to successively close secondary switches I31, I38 and I40 and to hold them closed until releasing coil I H is actuated and successively opens the circuits beginning with switch I40, then I38 and finally I31. The three way solenoid coil I36 is in circuit with starting switch I22, by connectors I43, I44, I45 and I46, coil I36, connector I41, to ground. The secondary switches or circuit controllers of the solenoid effect the working of cer- BEST AVAILABLE com tain elements as follows: Switch I31, actuated on the first push of the starting button closes a circuit from lead I32, through a control switch I50, through the solenoid air valve H1 and to lead I30 through ground thus forcing the roller electrodes down against the work; the second operated switch I38 has a connection I52 to a coil I53 of a relay I54, controlling the crane drive motor 69 and closing a circuit therethrough when coil I53 is energized and the cross-bar I66 is raised from back contact I56, the other end of which coil is connected to line I30 as at I55. Relay I54 has a common back contact I56 which is only engaged when cross-bar I66 is dropped by opening of the circuit through coil I 53 and is thus arranged to prevent operation of the crane motor reversing relays I 51 and I58 until after the crane motor has been disconnected from the line.

The motor reversing relay circuits include connector I60 from the contact I56 to coil I6I of relay I58, then through connection I62 and I63 through manual "reverse" switch I24, to line I30, or through lead I64, through automatic limit switch I65 to line I30. Actuation of relay I53 by the switch I38 raises cross-bar I66 of the relay from contact I56 and closes a circuit from lead I 32, through the relay I53, through I61, contact I69 or I15, depending upon the actuated position of cross-bar I 59 of the relay, relay I51, connector I10 or IN, to the crane motor 69, or through connector IN or I10, through relay I51, contact I13 or I14, connector I12, relay I53, to lead I3I. If reverse operation of the crane or traveling carriage is desired, the relay I 51 is actuated to raise the cross-bar from contacts I69 and I13, and into engagement with contacts I14 and I15, respectively, the lines I12 and I 61, For forward running the contact bar I 59 is dropped and the circuit is reversed as will be clear. The actuation of relay I51 to drop 'bar I59 is accomplished either byactuation of manual switch I26, or of automatic limit switch I16. In this case the circult is from lead I32, relay I53, contact I56, connector I 60, releasing coil I11 of relay I58 (opening its switch by dropping its cross-bar I 19) then through connector I18, eitherthrough switch I16 or I26 to common line I30. The dropping of cross-bar I19 opens the circuits I43, I39, contact II9, bar I19, contact I29, coil of I51. This drops bar I59 into the lower position.

It will be clear that actuation of either reverse or forward manual switch, or the appropriate automatic limit switches will actuate relay I58 in one direction or the other, which in turn actuates relay I 51 to reverse the carriage motor circuits from what they had been at the instant the particular switch was closed. It will be understood that the reversing of the current to the carriage or crane motor should stop the motor, and that, except for manual stoppages, a predetermined reverse or forward motion of the carriage should be initiated by the closing of one limit switch at one end of the carriage track and maintained until the opposite limit switch is actuated at the completion of the carriage travel. To this end relays I and I8I are provided, of which the latter has a contact bar I82, which in the released position shown is in contact with contact I89 in circuit with coil I6I of relay I58 by means of the connectors I62 and I63. The coil I84 of relay I8I is in circuit with connector I83 at one end and at the other by connector I85 is connected to relay releasing coil I81 of the relay I8I. Coil I81 is in circuit with connector I18 of the forward switch circuit already described, by connector I88 and the latter also contains a contact I90 in position to be engaged by the contact bar I82 of relay I8I when the relay coil I84 is actuated to raise the contact bar. The contact bar I82 of relay I8I is in circuit with coil I9I of relay I80, by connector I92. Relay I80 has two contact bars, respectively I93 and I94 so as to simultaneously close, or open, two distinct circuits, as follows: Contact arm or bar I93 engages a contact I95, connected by wire I86 to connector I85 of the coils of relay I8I, and contact I96, joined to connector I44 joined by connector I43 to lead I 32, at one end, and leading to wire I45 and start switch I22, and operating coil I36 of the three position relay I35 through wire I41 to line I30 at the other, and contact bar I94 engages a contact I98 joined by wire 200 to release coil I4I of the three position sequential relay I35, then through wire 20I and I41 to line I30, or through wire 202, to one side of release or neutral switch 203, the cross-bar or contact 204 of which moves to circuit closing position engaging contacts I05 and I06 whenever operate coil I36 is energized, and the respective secondary circuit controllers I31, I38 and I40 in that order are closed, and from "release contact I06, by wire 201 to the release coil 208 of relay I80, by wire I44, to wire I43. Additional connectors and contacts are provided, as follows: to contact 2I2 of relay I34, by wire 2I3 from connector I44. From connector I44 through "stop" switch I20, by wires 2I4, 200, to release coil I of the relay I35. The cross-bar I19 of relay I58 is moved into latched engagement with contacts I I 9 and I20 to close a circuit from lead I32, wires I43 and I39, cross-bar I19, wires I49, through signal relay 3 to line I30, and through coil of relay I51 to line I30. The relay thus is energized to reverse the circuits through the crane or carriage motor. When relay 3I I is energized lamp I21 gives reverse indication; when relay 3 .is deenergized lamp I25 gives forward indication.

It will be agreed that there will be numerous occasions whereupon it will be desirable to move the carriage relative to the work, or its supporting table without actually welding, and that means to cut out the welding would be valuable. To this end the circuit from lead I32, through the last operated switch I40 of the three circuit relay I35, is by a wire 2I5, through a toggle or other manually operated switch 2I6, through wire 2I1, coil 2I8 of relay I34 to ground. Obviously, when the toggle switch 2I6 is closed, the welding is automatically initiated upon the third push being applied to the start" button I22.

It is thought that with the discussion just preceding, the operation of the system and the functions of the purely diagrammatic disclosure will be clear. In brief, the diagram purports to indicate a situation in which the direction of travel is to be forward. Instantaneously limit switch I16 is held closed by'the carriage which has actuated it and releasing coil I11 has dropped opening reversing relay I58. The timer motor is connected as shown on the drawings. After the air valves have been started by the first push on start button, closing switch I31 of relay I35 and forcing the welding rollers against the work, the next successive push closes switch I38, operating coil I53, raising cross-bar I66, closing circuit through the leads of relay I51, through leads I10 and I H to the crane or carriage motor, starting the crane on its forward drive. Thereafter the button I22 can be given its third push, switch BEST AVAILABLE COP:

I40 of relay I is closed and the welding operation begins. The operation continues until either the stop switch I20, reverse switch I24, or limit switch I65 is actuated.

If the "stop" button is pushed a circuit is closed from lead I32, wires I43, I44, switch I20, wires 2, 200, release coil I of relay I35, wires 20I, I41, to ground. The "release coil I4I instantly opens relay I35, progressively opening switches I40, I38 and I31, in that order, so that the welding current is never "on when the carriage stops, or when the welding rollers are raised from the work.

If the "reverse switch I24 or limit switch I65 is actuated, the same result is secured except that the limit switch I65 remains closed until after the carriage has moved away from the limit switch on its return trip. In view of this protracted closing of the limit switch it is necessary that the control he transferred to the opposite limit switch I16. With the parts in the position shown, except for the fact that limit switch I65, or reverse switch I24, has been closed, a circuit is closed by the reversing switch as follows; from lead I32, by wires I43, I44, coil I9I (raising the contact bars of relay I80), through wire I92, relay I8I, contact bar I82, contact I89, wire I83, limit switch I65, or through wire I63, and reversing switch I24, to line I30. Energization of coil I9I of relay I80, raises cross-bar I93 and latches it in raised position, closing a circuit from lead I32, through wires I 43, I44, contact I96, bar I93, contact I95, wire I86, through coil I84 of relay I8I, raising cross-bar I82 out of contact with contact I89, to latched position in contact with contact I90, through wire I 83, and switches I65 or I24, to line I30.

It will thus be apparent that the control has been transferred to the circuit of the forward" switches, although nothing happens in that circuit until a switch is closed in that circuit. Of importance in this connection is the fact that the actuation of relay I80 has also raised cross-bar I94 and closed a circuit from lead I32, wires I43, I44, contact 2| I, through cross-bar I 94, contact I98, wire 200, release coil I4I, wires 20I, I41, to line I30. automatically opens all of the switches in the sequential relay and stops everything. The carriage stops in engagement with limit switch I65,

holding it closed until the carriage moves in the reverse direction. The opening of switch I38 of relay I35, breaks the circuit in the coil of relay I53, closing a circuit from lead I 32, through relay I53, cross-bar I66, contact I56, wire I60 through coil I6I of relay I58, raising the cross-bar I19 to latched position in engagement with contacts I I9 and I29, through wires I62, I64, the reversing or limit switch to ground. Simultaneously a circuit has been established from lead I32, through wires I43, I39, contact II9, contact bar I19, contact I29, of relay I58, through wires I49 and I59, and the coil of relay I51, thus raising cross-bar I59 into engagement with reversing contacts I 14 and I15, although the crane motor is not at that time energized.

It will be seen that at this time, with everything stopped, relays I80, I 8I and I58 will be latched in their up" positions, and relay I51 will be electrically held up.

- If now the cycle is started anew by pushing the start button or switch three distinct times the coil of relay I53 will be energized and thecross-bar I66 will be raised to close a circuit through the crane motor through relay I51.

The release coil successively and The first operation of the sequential relay I35 closes the neutral switch 203 which completes the circuit; line I32, wire I43, coil 208 of relay I80, wire 2I0, contact I06, cross-bar 204, contact I05, wire 202, line I 30. This releases the latch 'of re- -lay I80 and opens the circuit to the releasing coil I4I of sequential relay I 35 thus making it possible for the sequential operating coil I 36 to perform its operations.

When the limit switch.I16 or forward switch I26 is actuated in due course coil I9I will be actuated to close relay I80; this will actuate release coil I4I of relay I35, and when relay I35 has opened contact I 38, relay I53 will drop out. The opening of relay I53 will make up the back contact I 56 which will actuate the release coil I11 of relay I58 to drop its contact bar and the circuit through the coil of relay I51 will be opened and the relay will drop to reverse the connections to the carriage motor. When relay I 80 closes the release coil- I81 of relay II will be actuated dropping out relay I 8|. Relay I 80 will be unlatched on the first operation of the sequential relay I35 which restores all relays to the forward operating condition. This is believed to be clear.

The operation of the apparatus, in rsum, starts with the parts shown in the diagrammatic position, it may be presumed, with all of the relays open and no circuit closed and with the carriage at the rear end of the table. The table I0 is positioned laterally to bring selected rods 30 in substantial alignment with the electrode rollers according to the pitch of corrugated sheet to be welded, and in accordance with the particular-apertures or 44 in the guide plate I5, as predetermined by the plate positioning,.andthe anchoring of pin I6 therein. At this juncture the previously corrugated sheet 32-is laid upon the grid with appropriate rods 30 seated within the respective corrugations. This is facilitated by the restrained floating characteristics of the rods 30, enabling such slight lateral shiftingas will permit proper seating of a rod in a corruga-v tion. This may be accomplished by dropping the weighted rollers upon the corrugated sheet, until seating is accomplished.

Then the flat sheet 39, of the desired material, illustratively hard stainless steel is superimposed on the corrugated sheet and has its free ends secured in the respective clamps in the stretching or tensioning devices at the ends of the table, and the jack, or other tensioning devicehis actuated so as to subject the sheet to tension substantially in the plane of the peaks of the corrugation of the corrugated sheet. This removes the bumps, indentations and other irregularities normally present in the unrolled sheet of steel. he We hted rollers are then caused to rest upon the assembled sheets and to force them into intimate uniform contact over all of the contacting areas outlined by the rollers. It will be evident that at this point, and during the weldingoperation to follow, the flat sheet is exactly tangential to the corrugations of the lower sheet, and'that the corrugations have a rod 30 in intimate contacting relation in the peak of the corrugation so that even though the flattened contact area of a roller electrode should by mischance not be exactly centered relative to the crest or peak of the corrugation beneath the flat sheet, the weld spot will still take place exactly on the peak of the corrugation.

The sequence of button pushing is initiated, and the welding carriage travels longitudinally of the table and the superposed work and simul- BEST AVAILABLE COP\ taneously welds two rows of welds. Usually the rows are adjacent and the welding current travels from the secondary coil down through one weld roller, through the work and into the bed ofrods, through the work and up the other weld roller, to the secondary coil. At the conclusion of a row or rows of welds the carriage is stopped, and

the table and work are shifted laterally to register the welding rollers with the next pair of corrugation supporting rods and the travel is repeated in reversed a direction. Obviously the rate of speed of thecarriage and the rate of the welding timer are predetermined so that the resultant weld lines are composed of predeterminedly spaced or overlapping spots.

' Among other advantages of the instant invention is the formation of flat work which is later to be bent, in such a manner that the bend is accomplished without undue stressing or flattening of the convex side of the bend. Assume the entering edge of an airplane wing, for instance, as shown at Fig. 8. It is desirable that the metal 220 comprising the outer skin of the entering edge be continuously curved which requires that the portions 22l between corrugation peaks 222 and 223, for instance, also be continuously curved on the proper curvature. If, how ever, the work is finished and welded on the instant device, as explained heretofore, the portions of metal between corrugation peaks is stretched and is held flat, owing to the curvature so that the entering edge comprises a series of flats between corrugations, in place of the continuous curved surface desired. The simple device for securing this result is shown in Fig. 7, in which the valleys or upwardly presented corrugations between rods 30 support elongated independent deforming rods 224 upon which the relatively uncorrugated sheet is superimposed and in which a shallow arcuate bump or swelling 225 is formed in the area 22| between adjacent corrugation peaks 222 and 223. Usually but one or two of the metal crowding rods are used at a time. The eifect is to crowd extra metal (225) into the space between corrugation peaks, without causing the metal to flow, which is later pulled into the continuous curve shown in Fig. 8, when the bending is accomplished. After the sheets are welded by weld lines on each side of an independent rod 224, the latter is pulled out axially against the frictional resistance caused by its engagement with each sheet, thus leaving the crowded elongated portions 225 in the composite sheet.

The curvilinear grid alternatively proposed will secure similar ends, of itself, if the curve is that desired for the finished work.

Although two rollers in series through the work and the supporting grid are shown, it will be understood that a single roller could be resorted to, or a larger number could be used, as shown for instance, in Fig. 16. In this purely diagrammatic disclosure, the primary 3||l of a welding transformer, is disposed in operative relation to the secondary coil 3. A series of welding rollers, illustratively 3| 2, 3|3, working as one pair, and 3H and 3| 5, working as another pair, are provided suitably for juxtaposed operative engagement with work sheet 39 and corrugated reinforcement 32. Roller 3| 2 is connected to a terminal 3| 6 of a switch 3|! connected to one end of the secondary coil 3| i, while roller 3| 3 is connected by lead 3|9 to a pole 3|B of a switch 320, in turn connected to the other end of secondary coil 3 by wire 32L When the switch 320 is on pole 3| 8, and the coupled switch 3|! is on pole 3| 6, the secondary or welding current is from the coil 3| I through switch 3| 1, roller 3|2, the work, through the supporting grid (not shown in Fig. 16) through the work, through roller 3|3 to the coil 3| I, through switch 320. Roller electrode 3| 4 connects by lead 322 to a pole or switch terminal 329 of switch 3| 1, and roller 3|5 connects by lead 323 to the pole 324 of the switch 320. When rollers 3|2 and 3|3 are in series in the welding circuit, obviously because of the switch dispositions, electrodes 3 and 3|5 carry no welding current. Reversal of switches 3|| and 320 cuts out the first pair of roller electrodes, and places rollers 3H and 3|5 in series with the transformer secondary. To move switches 3|! and 320 from pole to pole as desired a timed means, such as a motor driven crank 325 drives switches 3H and 320 through pitmans or connecting rods 326 and 321. The motor driven member 325 is synchronized with the timer motor 4 operatively associated with the transformer in any desired manner so as to reverse the polarity of the switches between timed impulses. Obviously the alternate use of the pairs of rollers with a common tran -former, establishes slightly staggered welding spots in adjacent or contiguous rows of spot welds, but accomplishes twice the work in the same time and in the same travel of the carriage. Obviously this can be modified as desired so as to introduce more rollers, either single rollers, or pairs thereof.

It will be understood that the instant disclosure is purely illustrative and in many cases merely diagrammatic, and is obviously susceptible to many modifications. It will also be understood that all necessary auxiliary devices such as are common in the welding art may be provided with the instant invention. For instance it is contemplated that suitable means will be provided for spraying water upon the work adjacent to the welding rollers, and that this may be controlled by valve operated either manually or automatically.

We claim:

1. A welding apparatus comprising a table for supporting the work, a grid of rods mounted on the table and comprised of spaced parallel electrically interconnected rods, means enabling lateral adjustments of the table in a direction transverse to said grid, a welding roller the axis of which is substantially normal to a rod of the grid, the welding roller arranged to engage work on a rod, and means for securing longitudinal relative motion between said roller and a rod.

2. A welding apparatus comprising a traveling carriage, means supporting the carriage for horizontal movement, a welding rollermounted on the carriage, a table for supporting the work during the rolling movement of the electrode, means for holding the work in a predetermined position relative to the contact area of the rolling electrode during welding and said means comprising a rolling clamp arranged to hold parts of the work laterally spaced from the welding area of the work in a predetermined position to the welding area of the work to secure a predetermined contour to the finished welded work.

3. A welding apparatus comprising a table for BEST AVAILABLE COPi ing carriage, means for supporting the'ca-rriage for horizontal movement, means on the carriage for driving same on the supporting means, a

welding roller on said carriage, means for moving said roller vertically, and weighted rollers extending transversely of and movable on said carriage and disposed on each side of the welding roller and of such length as to exert pressure on the work laterally appreciably spaced from the welding roller. a

5. In welding apparatus, a traveling carriag a primary guide frame on the carriage, an elec trode roller operatively supported on the guide frame, means for moving the roller vertically relative to said frame. a secondary guide frame on the carriage, an electrode roller operatively supported on the secondary guide frame, means for moving the last mentioned roller vertically relatively to the secondary guide frame, and means for securing lateral relative movement of said rollers.

6. In welding apparatus, a fixed support, a table, a traveling carriage mounted on the support, means for moving the carriage at a predetermined but variable speed relative to the table, a welding timer for producing timed welding impulses, a welding roller electrode operatively electrically associated with the timer and with the carriage, the whole so constructed and arranged that a series of spot welds can be effected upon work mounted on the table with spaces between welds variable with and as a function of the carriage speed as the rolling electrode moves relative to work on said table.

7. In welding apparatus, a table comprising a plurality of substantially parallel cylindrical rods extending longitudinally of the table. and means for supporting same against yielding under welding pressures.

8. In welding apparatus, a table comprising a plurality of substantially parallel cylindrical rods ing a rigid grid of substantially flat inflexible strips underlying and reinforcing the respective rods, and means holding the rods and strips toether against vertical relative movement while permitting slight lateral relative adjustment.

10. In welding apparatus, a support, a carriage mounted on the support, a table relative to which the carriage has longitudinal travel, said table having a surface comprised of spaced parallel cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a pair of welding rollers substantially vertically adjustably mounted on the carriage and operatively aligned with respective rods, means for passing a welding current through work engaged between a roller and a rod.

11. In welding apparatus, a support, a carriage mounted on the support, a table relative to which the carriage haslongitudinal travel, said table having a surface comprisedof spaced parallel cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a pair of welding rollers substantially vertically adjustably mounted on the carriage and operatively aligned with respective rods, means for passing a welding current through work engaged between a roller and a rod, arms on the carriage,

I a weighted roller extending transversely between the arms of appreciably greater length than the respective electrode rollers, and means for moving the arms to dispose the roller operatively on the work on the rods on each side of the line of welds from a roller electrode.

12. In welding apparatus, a support, a carriage mounted on the support, a table relative to which the carriage has longitudinal travel, said table having a surface comprised of spaced parallel cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a pair of welding rollers substantially vertically adjustably mounted on the carriage and operatively aligned with respective rods, means for passing a welding current through work engaged between a roller and a rod, arms on the carriage, a weighted roller extending transversely between the arms of appreciably greater length than the respective electrode rollers, and means for moving the arms to dispose the roller operatively on the work on the rods on each side of the line of welds from a roller electrode, and a second weighted vertically movable roller on the other side of said roller electrodes from the first mentioned roller.

13. In welding apparatus, a support, a 'carriage mounted on the support, a table relative to which the carriage has longitudinal'travel,

said table having a plurality of removable and replaceable surfaces each comprised of spaced parallel cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a pair of welding rollers substantially vertically adjustably mounted on the carriage and operatively aligned with respective rods of a given surface, means for passing a welding current through work engaged between a roller and a rod, and means for varying the lateral spacing between the electrode rollers to accordwith a change in effective spacing of said rods.

14. In welding apparatus, a support, a carriage mounted on the support, a table relative to which the carriage has longitudinal travel, said table having a surface comprised of spaced parallel cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a pair of welding rollers substantially vertically adjustably mounted on the carriage and operatively aligned with respective rods, means for pas'sing'a welding current through work engaged between a roller and a rod, and means operatively associated with the table for subjectingsuch flat sheet to endwise tension in substantial parallelism with said rods and maintaining the tension during welding movement of the carriage.

'15. A welding apparatus comprising a table, a grid of electrically interconnected parallel rods removably mounted on the table, a traveling carriage, a pair of substantially parallel welding rollers mounted on the carriage, means for securing lateral relative adjustments of the rollers to accord with the clearance between the rods of the grid, and means for moving the carriage and rollers longitudinally of the grid and table.

16. A welding apparatus comprising a table of BEST AVAELABLE COP\ appreciable length, means supporting the table for lateral shifting movement, a welding roller, means for securing relative longitudinal movement of the roller and the table, and means for synchronizing the shifting movement of opposite ends of the table to maintain a predetermined alignment with the welding roller relative movement.

17. A welding apparatus comprising a table for supportingthe work comprising a plurality of spaced substantially parallel horizontal rods electrically interconnected, a pair of welding rollers having each an axis substantially normal to a rod arranged for alignment with selected rods of a pair in electrical interconnection, said rods presenting toward the rollers transversely curved surfaces and means for passing a welding cur rent through one welding roller through the work, through a rod through the electrical connection between rods through the other rod of said pair and through the other of said pair of welding rollers after passing again through the work.

18. In welding apparatus, a table comprising a plurality of substantially parallel substantially cylindrical conductive electrically interconnected rods, supporting means for the rods comprising a rigid grid of substantially fiat surfaced strips underlying and reinforcing the respective rods.

19. In welding apparatus, a table, a pair of rolling electrodes, means securing longitudinal relative movement of the roller and table, means in front and behind the rollers relatively traveling with the rollers to hold the parts of the work laterally remote from the weld in a predetermined position relative to the part being welded to prevent warping and distortion.

20. In welding apparatus, a table comprising a plurality of substantially parallel substantially cylindrical rods extending longitudinally of the table, and means for supporting same against yielding under welding pressures including a rigid grid of substantially flat surfaced relatively inflexible strips underlying and reinforcing the respective rods, and means holding the rods and strips together against vertical relative movement while permitting slight lateral relative adjustment, said rods being continuously electrically interconnected.

21. In welding apparatus, a support, a carriage mounted on the support, a table relative to which the carriage has longitudinal travel, said table having a surface comprised of spaced parallel substantially cylindrical rods upon which a corrugated sheet can be disposed with rods in corrugations and with a flat sheet on the corrugated sheet, a plurality of welding rollers substantially vertically adjustable on the carriage and operatively aligned with selected rods, said rods being electrically interconnected, and means for pass- 7 ing a welding current through certain of the welding rollers the work and the grid of rods.

22. In welding apparatus, a support, a carriage mounted on the support, a table relative to which a the carriage has longitudinal travel, said table having a surface comprised of spaced parallel cylindrical rods upon which a corrugated sheet,

can be disposed with rods in corrugations and with an uncorrugated sheet on the corrugated sheet, a plurality of welding rollers adjustably mounted on the carriage and operatively aligned with selected rods, means for passing a welding current through work engaged between a roller and a rod, a rolling clamp comprising a weighted roller resting upon the work both before and behind the adjacent points of the roller and rod through which the current passes and extending laterally of such point so as to hold the corrugated and uncorrugated sheets in such juxtaposition as to cause the finished work to conform to a predetermined unwarped contour.

23. In welding apparatus, a table, a removable grid forming the surface of the table, said grid comprised of a plurality of parallel substantially rigid substantially flat surfaced strips, means con necting the strips electrically and physically in spaced relation, a plurality of substantially cylindrical rods juxtaposed upon the flat surface of the respective strips, each rod having a peripheral groove, clamp means engaging the respective strips and rods having a portion received in said groove to form a substantial cylindrical continuation of the surface of the said rod, said clamp means so arranged as to permit slight lateral shifting of the rods without breaking the electrical engagement with the strip, and said strips and rods being of electrically conductive material.

24. In welding apparatus, a table, a rolling electrode, means for securing longitudinal relative movement between the table and rolling electrode, a tensioning device for subjecting the work between the table and electrode to longitudinal tension during welding to obviate unevenreceive corrugated material, means on the table for subjecting uncorrugated material to tension longitudinally of the table while the uncorrugated material is juxtaposed upon the corrugated material, means for welding the juxtaposed materials, and a rolling clamp arranged to hold the juxtaposed corrugated and uncorrugated sheets in a predetermined position at points remote from the weld point to insure that the finished work conforms to a predetermined contour free from wrinkles as well as from warping.

26. In welding apparatus, a tensioning device for subjecting work to be welded to predetermined endwise tension during welding, with indicating means operatively associated therewith to predetermine the tension.

27. In welding apparatus, a support, a table mounted on said support and arranged for lateral movement thereon, a grid of rods removably mounted on the table and comprising the supporting surface of said table, a plurality of electrode rollers, means supporting the electrode rollers in alignment with rods of the grid, and means for varying the lateral spacing of the rollers to accord with variations in spacing of the rods of the grid, and means for securing relative rolling movement of the roller electrodes and the grid of rods longitudinally of the rods.

28. A method of welding sheets together which comprises supporting the sheets on a table, subjecting the superposed sheets to the compressing action of a rolling clamp at points spaced fore and aft and laterally of the instantaneous weld point to maintain a predetermined position of the points remote from the welding during welding, and then in welding the sheets together in a position predetermined by the rolling clamp.

29. A process of welding a relatively flat sheet to the peaks of round corrugations in a relatively corrugated sheet, which comprises associating a rod electrode having an upper substantially cylindrical surface longitudinally with the undersurface of the peak of a round corrugation, of superimposing the relatively flat sheet upon said peak, then of rolling a fiat-rimmed electrode roller along the relatively flat sheet in substantial alignment with said rod, and in passing a plurality of welding current impulses between the roller and rod through the peak of the corrugation and the superimposed sheet.

30. A process of welding round corrugated sheets to flat sheets which comprises applying corrugated sheets to a grid of substantially cylindrical rods fitting in the respective corrugations,

and in applying a flattened roller electrode to the superimposed flat sheet in alignment with a corrugation to. insure that the welding is on the peaks of the corrugations.

31. A method of forming a continuously curved reinforced section which includes positioning a rod between adjacent corrugations of a corrugated reinforcing sheet so that its peak extends beyond a plane common to the peaks of said adjacent corrugations, superimposing a relatively flat sheet upon the corrugated sheet and rod, spot welding the relatively flat sheet to the peaks of the corrugations adjacent to the rod to bend the sheet about the rod and to impart an initial curvature to the uncorrugated sheet, re-

and corrugated sheets.

32. A method of welding corrugated sheets to relatively uncorrugated sheets which comprises imposing a corrugated sheet upon a grid of rods with rods disposed in the respective corrugations,

in superimposing upon the corrugated sheet a relatively uncorrugated sheet, pressing the uncorrugated sheet firmly upon the corrugated sheet by a rolling clamp on each side of the instantaneous weld point, and in welding the sheets together between the rolling clamps.

33. A method of welding relatively corrugated and uncorrugated sheets together in a predetermined contour which comprises mounting the corrugated sheet on a table with rods in the re- "spective corrugations, superimposing upon the corrugated sheet a relatively uncorrugated sheet, subjecting the relatively uncorrugated sheet to tension, securing relative longitudinal movement of the composite sheet and a roller electrode, subjecting portions of the composite sheet remote from the instantaneous weld point to rolling pressure to maintain a fixed position of the adjacent sheets relative to the portions of the adjacent sheets at the weld point, and then passing a welding current through the work at the weld point. a

34. A welding apparatus for corrugated work comprising a table for supporting the work, said table comprising a plurality of longitudinally extending spaced substantially parallel horizontal rods the upper half substantially of each of which rods is substantially a semi-cylindrical bearing surface, with an air gap laterally between adja- 00 cent upper half portions into which gap upwardly presenting corrugations extend downwardly from a corrugated sheet while downwardly presenting corrugations nest upon rods on each side of a respective gap, a welding roller having a flat rim or the axis of which is substantially normal to said 25 moving the rod, and bending the combined flat at its contacting point being substantially tangential to the central bearing surface thereof and to a corrugation nested thereon.

35. A welding apparatus comprising a table for supporting the work, said table having a rigid rod supporting portion the upper surface of which lies in a common horizontal plane, a plurality of substantially cylindrical rods disposed longitudinally on said supporting portion in parallelism and in laterally spaced relation, a welding roller having a flattened rim disposed substantially symmetrically of a rod with the rim substantially tangential to the upper surface of said rod at its contacting point, and means for securing relative longitudinal movement of the roller and rod.

36. In welding apparatus, a table comprising a plurality of substantially parallel substantially cylindrical rods extending longitudinally of the table, means for supporting same against yielding under welding pressures comprising a rigid support having an upper surface in a common plane, with the rods mounted on the common" plane, means anchoring the rods to the supporting means while permitting slight lateral shifting thereof on said common plane to accord with inequalities and the like in the work.

3'7. In welding apparatus, a table, a rolling electrode, means securing longitudinal relative movement of the rolling electrode and table, means in front of and behind the roller relative-'- ly traveling with the electrode to hold the parts of the work laterally and longitudinally remote from the weld point in a predetermined position relative to the part being welded to prevent warping and distortion.

38. In welding apparatus, a table, a roller electrode, means securing longitudinal relative movement of the roller and table, a rolling clamp engaging the work laterally and-longitudinally spaced from the weld point to hold the parts of the work remote from the weld in a predetermined position relative to the part being welded to obviate warping, and means exerting tension on the work during welding.

39. In welding apparatus, a table, means anchoring the work to the table and subjecting it to longitudinal tension, a roller electrode, means securing longitudinal relative movement of the work on the table and the roller, an elongated weighted roller disposed'longitudinally respectively on each side of the electrode and bearing upon the work under tension to clamp the work to the table at points laterally and longitudinally spaced from the welding point so as to prevent warping and distortion.

40. In welding apparatus, a table, means mounted toward one end of the table for anchoring an end of the work, means mounted toward the other end of the table for engaging another end of the work, said second-mentioned means including a tensioning device whereby work engaged by both means may be subjected to tension longitudinally of the table, an electrode operatively disposed relative to the work on said table effective to weld the work during the maintenance of tension thereon.

CARL 1m GANAHL. THOMAS B. LAVELLE. 

